Technical Field
Embodiments of the present invention relate to a drive transmission unit, a fixing device with the drive transmission unit, and an image forming apparatus having the fixing device with the drive transmission unit.
Related Art
In an image forming apparatus such as a copier, a printer, a facsimile machine, etc., a toner image is formed on an image bearer based on image information. The toner image is transferred onto a recording medium and is fixed thereto by heat and pressure in a fixing device when the recording medium bearing the toner image thereon is conveyed through the fixing device.
The fixing device includes a fixing member, such as a fixing roller, a fixing belt, etc., with temperature maintained at a specified level and a pressing member brought in pressure contact with the fixing member. Thus, the fixing device fixes the toner image by conveying and heating the recording medium bearing the toner image thereon in a fixing nip formed between the pressing member and the fixing member brought in pressure contact with each other.
In this type of the fixing device, although a prescribed toner adhesion preventing system is employed to prevent adhesion of toner to a surface of the fixing member, a so-called offset unavoidably occurs sometimes. That is, toner borne on the recording medium slightly adheres to the fixing member when it is conveyed through the fixing device depending on image formation conditions, such as a type of recording medium, an image to be formed, installation environment of an apparatus, etc. Since the offset caused in this way (herein after also referred to as “offset toner”) remains on the fixing member and/or the pressing member pressed against the fixing member and may be reversely transferred onto the recording medium, degrading the image quality.
To solve such a problem, there are systems that include a cleaner pressed against the pressing member constituting the fixing device to collect toner adhering to the pressing member therefrom. As one example of the known cleaner, a belt-like cleaning web is used in such a manner that the cleaning web is pulled out from a spool that winds the cleaning web around itself and is taken up and collected by another spool after the cleaning web has cleaned the pressing member by wiping off a stain or the like from the pressing member.
When the recording medium is conveyed through the fixing member, cuts and stains, such as sheet dust, the offset toner, etc., are generated sometimes, thereby gradually roughening the surface of the fixing member. Especially, when the recording media of the same size are repeatedly conveyed through the fixing member, both lateral ends of the recording medium P serving as burrs, respectively, tend to roughen and damage corresponding portions of the surface of the fixing member. As a result, such stain and/or roughness on the surface of the fixing member generate a shiny stripe and unevenness in the image, thereby degrading image quality.
To prevent such degradation, it is possible to make a surface of the fixing member uniform by using a prescribed slider that slides along the surface of the fixing member thereby suppressing occurrence of the abnormal image of the shiny stripe or the like in the image formed on the recording sheet. As the slider, a polishing member to polish the surface of the fixing member of the fixing device to recover prescribed surface uniformity of the fixing member may be used. The polishing member is controlled to engage and disengage from the fixing member to maintain good polishing performance.
However, the above-described systems exhibit unstable driving force transmission when a driving force is transmitted from a driving source to the cleaner and the polishing member each serving as a driven member.